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THE UNIVERSITY 
OF ILLINOIS 


LIBRARY 


AMBER 


ITS PHYSICAL PROPERTIES AND 
GEOLOGICAL OCCURRENCE 


BY 
OLIVER C. FARRINGTON 
Curator of Geology 


FIELD MUSEUM OF NATURAL HISTORY 


CHICAGO 
1923 


maid 


ES ee Ce 


: ‘UFSNYV GQaAuvO " pon alee = ELL eT AG OT Ne ea 


FIELD MUSEUM OF NATURAL HISTORY 
DEPARTMENT OF GEOLOGY 
CHICAGO, 1923 


LEAFLET NUMBER 3 


Amber 
Its Physical Properties and Geological Occurrence 


Amber is a fossil gum of trees of the genus Pinus. 
Normally it is yellow in color, varying in shade, how- 
ever, from pale yellow to dark brown, and occasionally 
being whitish, greenish, or bluish. Very rarely, 
amber of a deeper green or blue color occurs. Such 
amber is always turbid or cloudy, the turbidity being 
due to the presence of numerous air-bubbles. The 
modification produced in rays of light by passing 
through the bubbles creates these colors. 

In transparency all graduations may occur in 
amber, between that which is perfectly clear and that 
which is wholly opaque. Of the cloudy forms, several 
varieties are distinguished in trade, the most im- 
portant being “bastard,” “bony,” or “osseous,” and 
“frothy” amber. Bastard amber is a somewhat turbid 
form of amber, but takes a good polish; bony amber 
is opaque, relatively soft, and does not polish well. 

The hardness of amber is 2 to 2.5. It therefore 
cannot be scratched by the finger nail, but easily 
and deeply with a knife. It is also brittle. Its specific 
gravity is scarcely greater than that of water, the 
exact specific weight being 1.05-1.096. It thus almost 
floats in water, especially sea-water. On being heated 
amber becomes soft at 150° C., and at 250° to 300° 
melts. It also burns readily and at a low temperature, 
a fact which has given rise to the name of Bernstein, 
by which the Germans know it, and to one of the 
Latin names for it, lapis ardens. Rubbed with a cloth 


[25] 


2 . FIELD MUSEUM OF NATURAL HISTORY 


oe EES o 
COOKS 
sees XXX YA 


FISHERMEN FISHING FOR AMBER 
FROM AN OLD DRAWING PUBLISHED IN 1677 


[ 26] 


—— = 1 


. ee 


AMBER 3 


it becomes strongly electric, attracting bits of paper, 
etc. Our word “electricity” comes from the Greek 
word elektron, which was their name for amber. 
Amber was one of the first minerals in which electrical 
properties were noted. Being a poor conductor 
of heat, amber feels warm rather than cold in the 
hand. In this respect it differs from most minerals. 
It is attacked but slowly by alcohol, ether, and similar 
solvents, a property by which it may be distinguished 
from most modern gums and some other fossil ones. 
In composition it is an oxygenated hydrocarbon, the 
percentage of these elements being in an average 
sample: Carbon: 78.94, Hydrogen: 10.53, and Oxy- 
gen: 10.53. The mineralogical name of amber is 
succinite, a word delivered from the Latin sucinum 
(“amber’’). One of its constituents is the organic 
acid called succinic acid. 

The present source of most of the amber of 
commerce is the Prussian coast of the Baltic Sea, 
between Memel and Dantzig, although it is found as 
far west as Schleswig-Holstein and the Frisian Is- 
lands, and even occasionally on the shores of Denmark, 
Norway, and Sweden. From time immemorial pieces 
of amber have been cast upon the shore in these lo- 
calities, and their collection and sale have afforded a 
livelihcod to coast-dwellers. Such amber is called “sea 
stone,” or “sea amber,” and is superior to that ob- 
tained by mining, since it is usually of uniform quality, 
and not discolored and altered on the surface. Owing 
to its lightness, this amber is often found entangled in 
seaweed, and the collectors are accustomed to draw 
in masses of seaweed and search them for amber. 
Amber so obtained is called “scoopstone,” because nets 
are sometimes used to gather in the seaweed. In 


marshy regions men on horseback, called amber riders, 


follow the outgoing tide and seek the yellow gum. 
It is also searched for by divers to some extent. 


[27] 


4 FIELD MUSEUM OF NATURAL HISTORY 


_ From the earliest times the title to this amber 
has vested in the State, and either its collecting has 
been done under State control, or, a tax is levied 
upon it. This tax is levied both on the amber that is 
mined, and that obtained from the sea, and brings a 
considerable revenue. 

Up to 1860 the methods of procuring amber were 
largely confined to obtaining it in the manner above 
noted. As it was evident, however, that the sea amber 
came from strata underneath, and that if, either by 
dredging or mining, these strata could be reached, a 
much larger supply could be obtained, exploration was 
carried on by mining methods with successful results, 
and the principal amount of the amber of commerce is 
now so obtained. The strata, as shown in the mines 
of Sammland, the rectangular peninsula of East 
Prussia, where most of the mining is carried on, are: 
First, a bed of sand; below this a layer of lignite with 
sand and clay; and following this a stratum of green 
sand, fifty or sixty feet in thickness. While all these 
strata contain scattered pieces of amber, it is at the 
bottom of the green sand layer that the amber chiefly 
occurs, in a stratum four or five feet thick, and of 
very dark color. It is called the “blue earth.” This 
stratum is of Tertiary age, and there can be no doubt 
that its amber represents gum fallen from pines which 
grew at this period, and whose woody remains are 
represented to some extent in the layer of lignite. It 
is probably true, also, that amber has been collected 
here from older deposits. 

One of the most interesting proofs of the vegetable 
origin of amber is the occurrence in it of insects, 
sometimes with a leg or wing separated from the body, 
showing a struggle to escape. It is obvious that the in- 
sect must have alighted upon the gum when that was 
in a viscid state and was held until covered by later 
exudations. These insects include spiders, flies, ants, 


[28] 


INSECTS IN AMBER. 


AMBER 5 


-and beetles, and even feathers of birds have been found 

thus preserved. Remains of plants, such as needles 
of conifers, oak leaves and other leaves, buds and 
blossoms, are also found preserved in amber. Indeed 
the variety of forms preserved in this way is so large 
as to indicate that the forests which produced the 
amber had a rich flora and fauna. As compared with 
modern forms, these plants and animals are found to 
belong to existing genera, but the species, with few 
exceptions, are peculiar to the region and period. 
Through the remains thus preserved, the amber de- 
posits have furnished important contributions to our 
knowledge of Tertiary life. 


Inasmuch as pieces of amber bearing such re- 
mains are valued more highly than ordinary amber, 
unscrupulous persons have at times found profitable 
employment in boring cavities into pieces of amber, 
introducing insects or other small animals into them, 
and having then filled up the hole with some modern 
gum of the same color, or fused the opening over, have 
placed them upon the market. It is probable that 
all amphibious or marine animals seen in amber have 
been introduced this way. 


Amber, often of greater beauty than that from 
’ Prussia, comes from Sicily. The beauty of the Sicilian 
amber consists in the variety of colors it displays, 
blood-red and chrysolite-green being not uncommon; 
and in the fact that these often exhibit a fluorescence, 
glowing within with a light of different color from the 
exterior. Chemically the Sicilian amber is not the 
same as the Prussian, as it contains less succinic acid, 
and it is somewhat more soluble. In other respects 
it is not essentially different. It occurs chiefly on the 
eastern and southeastern coasts of the Sicilian islands, 
being washed up in a manner very similar to the 
Prussian amber. 


[29] 


6 FIELD MUSEUM OF NATURAL HISTORY 


Amber has been found in several places in the 
United States, but little has proved of commercial 
value. It is mostly connected with the Cretaceous 
glauconitic, or green sand deposits of New Jersey, 
fragments being frequently found there. This amber 
is of yellow color, but not so compact or lustrous as 


foreign amber. Amber has also been reported from - 


the marls of North Carolina, some of the coal-beds 
of Wyoming, and in connection with lignite in Alaska. 
In the latter region the natives are said to carve it 
into rude beads. 

Besides Prussia and Sicily, amber occurs in small 
quantities in several other countries of Europe, such 
as near Basle, in Switzerland; near Paris, in France; 
and near London, in England. It is also found in 
many parts of Asia, these localities being a source of 
supply to the Asiatic countries, such as China and 
India. Occasionally amber is obtained from Mexico 
which has the beautiful fluorescence of the Sicilian 
article, but the exact locality whence it comes is in 
doubt. 

Besides the counterfeiting of inclusions of amber 
there are several substitutes for the gum itself. These 
are chiefly celluloid and glass, the former being danger- 
ous if used in the manufacture of smoker’s articles, 
on account of its inflammatory character. Celluloid 
can be distinguished from amber by the fact that 
when rubbed it does not become as electric, and gives 
off an odor of camphor instead of the somewhat aro- 
matic one of amber. Celluloid when dipped in hot 
water also gives an odor of camphor. It is also 
quickly attacked by alcohol, or ether, and when 
scraped with a knife, gives a shaving rather than a 
powder, as amber does. Amber, as already noted, is 
but slowly attacked by alcohol. Glass can be distin- 
guished from amber by its cold feel and greater hard- 
ness and specific gravity. 


[30] 


—— Save 


AMBER 7 


Besides these substitutes, it has been found pos- 
sible by heating and pressing scraps of amber not 
large enough for carving, to make them into a homo- 
geneous mass, which is sometimes sold as amber and 
sometimes as amberoid. 

Amber is worked to desired shapes by turning it 
on lathes, or by cutting by hand. By heating it in - 
linseed oil it becomes soft, so that it can be bent, and 
often all opaque spots can be made to disappear. It 
can also be colored during this treatment. 

Nearly one-half of the total production of amber 
is devoted to the manufacture of articles for the use 
of smokers, such as cigar and cigarette-holders, mouth- 
pieces for pipes, etc. Ornamental objects in great 
variety are also manufactured from it, the commonest 
of such articles being beads, rounded or faceted and 
perforated so that they can be strung together for 
necklaces, bracelets, rosaries, etc. These find sale in 
all parts of the world, the tastes of people of different 
countries being said to vary as to the kind of amber 
desired. Thus in Russia and France, for example, the 
fine bastard amber is preferred, in Holland and China 
the clear variety is wanted, while in West Africa the 
demand is for the semi-osseous kind with a brownish 
tinge. Pressed amber is suitable for cheap, relatively 
bulky articles, but is not adapted for fine manufac- 
tures, since after a time it has a tendency to turn white. 
The use of amber for varnish is another important 
utility, impure or small pieces being chiefly employed 
for this purpose. 

Specimens illustrating many of the features of 
amber enumerated in the preceding pages may be seen 
in Hall 34 of the Department of Geology of the Museum 
in a case located at about the center of the hall. 


OLIVER C. FARRINGTON. 


[31] 


CONGLOMERATE OF AMBER DROPS. 


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